The McCain Institute for International Leadership hosted a debate at the George Washington University’s Jack Morton Auditorium on Tuesday, pitting experts in opposite corners of the ring to discuss the effectiveness of the interim agreement to limit Iran’s nuclear activities in exchange for monetary aid and sanctions relief.

Ambassador Kurt Volker led the program with introductions and former CNN White House Chief Correspondent Jessica Yellin moderated the panel.

Sen. John McCain, R-Ariz. addresses the audience at the debate.

“I thank all of you for being here and thank you for this very important discussion,” Sen. John McCain, R-Ariz., said. “These four individuals are highly qualified to discuss this issue. This is something that has been with us for some period of time, and I think this will continue to be a topic of great debate and discussion, not only in the Congress of the United States, but in places all over the world.”

While the skeptics—Deputy Editor of the Wall Street Journal Bret Stephens and Foundation for Defense Democracies Senior Fellow Reuel Gerecht—called for a firmer stance that draws a red line to halt all enrichment with the threat of military action from the U.S. Administration, with support from other P5+1 countries, including Germany and the world powers that are permanent members of the UN Security Council, the U.K., France, Russia and China.

“Essentially what we have to do is not look at the ideal alternative to a nuclear deal with Iran, but what are the realistic alternatives to this current deal,” Mr. Sadjadpour said in an opening statement. “In an ideal world we could force Iran to dismantle its entire program and agree to zero enrichment of uranium, but realistically that isn’t going to happen.”

He warned that forcing a rigid approach could lead to a nuclear-armed Iran and that conservative hardliners in Tehran would put their foot on the “nuclear accelerator.”

Mr. Einhorn agreed, calling the interim deal, or “Joint Plan of Action,” that was determined during talks between the P5 +1 in Geneva in 2013, a “promising start” because it puts the Iranian nuclear program on hold for the first time in more than a decade.

The deal also allows an “open window” into Iran through daily access to uranium enrichment facilities and increased monitoring of centrifuge production plants, where nuclear power is developed, he said.

“We got a very good deal,” Mr. Einhorn said. “Estimates are that the total sanctions relief that Iran will get is about $7 billion, and during the same six-month period they will go $30 billion deeper into the hole because of lost oil revenues.”

Mr. Gerecht called the deal naïve and urged an approach that marries diplomacy with the threat of military action to get the best deal possible, calling 2014 “the year of fear.”

“If we get 12 months down the road and the Iranians have actually agreed to roll back their program in a serious way, I’d be the first to say the JPA is serious, but it’s not,” Mr. Gerecht said. “To say that we paid very little is true. We did pay very little, and we got less.”

Mr. Stephens said that thus far there has not been evidence that Iran will agree to halt the program, which should be the ultimate goal. The stipulations of the current deal will allow a “contained” Iran to retain its enrichment program and ability to reject inspections of facilities.

“The lesson that we learned in Iraq was not that we overhyped intelligence, it is that our intelligence agencies get it wrong time and again when it comes to anticipating nuclear proliferators and nuclear breakouts,” Mr. Stephens said. “There is this line out there that we will have perfect intelligence and we will know well in advance when Iran decides to break out, but that has simply not born out over 60 years of failure to anticipate proliferation.”

He was also critical of the U.S. perspective on the Iranian nuclear operation, which he said is rooted in the U.S. experience with a “fast break out,” or quickly developing and deploying nuclear weapons. In contrast, he said, Iran and other nations are more concerned with a “wide break out,” wherein they amass power and weaponry and wait for the right opportunity to strike.

Mr. Einhorn was bullish about the ability to establish a good monitoring regime in Iran that offers fair access to facilities. He said that the use of military force prior to any violations of the agreement would accelerate Iran’s nuclear program and lack credibility.

However, he added, should Iran violate the terms of the JPA, a pre-authorization from Congress that would allow the administration to deploy a military strike would add to U.S. credibility.

“I think that credibility was reduced when President Obama first went to Congress to seek authorization in the Syria case and Congress balked and the American people balked,” Mr. Einhorn said. “Prior authorization in the wake of an agreement would be a very powerful and credible motivator for Iran to comply with the agreement.”

Though they disagreed on the means, both parties were adamant that Iran’s nuclear capabilities must be fully disclosed and ultimately eliminated.

“The reason we are talking about Iran is because of the nature of that regime,” Mr. Stephens said. “It’s scary, and we can’t let them get weapons that are equally scary.”

“Know thine enemy,” Mr. Gerecht added. “I think we have to establish that unless we bring more force into these negotiations, getting a good deal, a deal that can actually stop the nuclear weapons program, is not possible,” he said.

Mr. Einhorn agreed but within limits.

“It would be a terrible, terrible thing to let Iran have nuclear weapons, and I agree that we should go to great lengths to stop them including use of military force, but before we use military force we have to make every effort to see if diplomacy will work.”

Despite the thorough discussion, the question of whether the U.S. stance on Iran’s nuclear program and the JPA will be effective will not be resolved until a final deal is reached.

“We have not settled this debate, but ‘it is better to debate a question without settling it than to settle a question without debating it,’” Mr. Sadjadpour said, quoting philosopher Joseph Joubert.